Indirect microbial detection

• US 4,264,728 A
• Filed: 08/17/1979
• Issued: 04/28/1981
• Est. Priority Date: 08/17/1979
• Status: Expired due to Term

• Current Assignee: United States Of America As Represented By The Administrator Of The National Aeronautics And Space Administration
• Original Assignee: United States Of America As Represented By The Administrator Of The National Aeronautics And Space Administration
• Inventors: Wilkins, Judd R.
• Primary Examiner(s): Hruskoci, Peter A.
• Application Number:
  US06/067,596
• Time in Patent Office: 620 Days
• Field of Search: 23/230 B, 204/1 T, 204/195 P, 204/195 B, 210/96.2, 422/68, 435/29, 435/30, 435/34, 435/291, 435/817, 435/5
• US Class Current: 435/5
• CPC Class Codes: C12M 41/36 of biomass, e.g. colony counters or by turbidity measurements electrooptical investigation of individual particles G01N15/14, flow cytometers G01N15/1404

Abstract

The growth of microorganisms in a sample is detected and monitored by culturing microorganisms in a growth medium and detecting a change in potential between two electrodes separated from the microbial growth by a barrier which is permeable to charged particles but microorganism impermeable.

Claims

1. An indirect method for detecting substances which influence microbial growth, which comprises:

separating a growth medium suitable for microorganisms into two compartments by a first semipermeable membrane barrier that is impermeable to microorganisms;

providing at least one additional semipermeable membrane barrier in one of the compartments and inoculating this compartment with microorganisms;

placing two electrodes in the other of the two compartments;

maintaining said electrodes in fluid or gaseous contact with said microorganisms;

bringing the compartment containing microbial growth into contact with an environment containing at least one substance that influences microbial growth and is permeable to the one additional semipermeable membrane; and

detecting and monitoring the change in potential between the two electrodes with a potentiometer having an impedance equal to at least one megohm to detect the substance which influences microbial growth in said environment.

2. The method of claim 1 wherein the environment substance influencing growth is selected from the group consisting of toxins, bacteriophages and water pollutants.

3. Apparatus for indirectly detecting and measuring microbial growth comprising:

a container;

a first chamber in said container housing a microbial growth medium and containing microorganisms said first chamber being provided with at least one semipermeable membrane in a sidewall thereof to permit microorganism growth influencing environment to contact the microbial growth medium;

a second chamber in said container housing a microbial growth medium;

a semipermeable membrane barrier impermeable to said microorganisms disposed between and maintaining said first and second chambers separate;

a pair of electrodes disposed in said second chamber and embedded in the said microbial growth medium;

an electric circuit connected to said pair of electrodes;

detecting means connected to said electric circuit to detect changes in electrical potential between said pair of electrodes;

said detecting means being a potentiometer with an impedance equal to at least one megohm;

whereby, microbial growth in said first chamber will produce charged particles that permeate said semipermeable barrier to contact said pair of electrodes and cause a change in electrical potential therebetween that is detected by said detecting means.

4. The apparatus of claim 3 wherein said potentiometer is connected to a strip chart recorder that permanently records the changes in electrical potential between said electrodes.

5. The apparatus of claim 3 wherein said microbial growth medium is selected from the group consisting of:

brain-heart infusion, trypticase soy broth (TSB), trypticase soy broth +CO₂, phenol red broth base +1% glucose, and litmus milk.

6. The apparatus of claim 3 wherein said first and said second chambers are provided with a separable threaded joint connection.